Suppose you want to buy a pair of shoes that have a retail price of $80. You have a coupon for $15 off your entire purchase. Also, as a rewards card holder for the shoe store, you are entitled to 20% off your entire purchase. To find the final cost of the shoes, the $15 coupon can be applied first and then the 20% discount, or the 20% discount can be applied first and then the $15 coupon. Which combination of discounts gives you the better deal?

How can the process of applying the discounts one at a time be reflected in a single expression to represent the correct order?